I knew there were two variants out there, but was not aware there are actually three! Seems so strange to me that they would make this many changes. Even the font looks slightly different (pics not mine - borrowed for this comparison only - hope that's ok):

Caseback variant 1 (waterresistant, shockproof, antimagnetic):

Caseback variant 2 (waterresistant, shockproof, sapphire crystal):

Caseback variant 3 (senator sixties, automatic):

Does this seem odd to anyone else? Is this correct? I'm sure there is a method to the madness here, but I can't figure it out. Especially over the course of such a relatively short lifespan!